Researchers discovered death and diseases of the heart or blood vessels in the brain are more likely to affect people who had more than eight hours' sleep a day compared to those who slept for between six and eight hours.

The study looked a data from 116,000 people aged between 35 and 70 in 21 different countries.

When they returned at an average of eight years later, they found 4,381 deaths and 4,365 "major cardiovascular events".

Participants who slept a total of eight to nine hours a day had a 5% greater risk of suffering such an incident than those who slept six to eight hours.

The danger rose to a 17% higher risk for people sleeping between nine and 10 hours a day while those sleeping more than 10 hours a day had a 41% increased risk of cardiovascular disease or death.

The international team wrote in the European Heart Journal: "Sleep is essential to human health, and people spend about a third of their hours sleeping. It is increasingly regarded as an important lifestyle behaviour that can affect cardiovascular disease (CVD) and death."

Co- author Professor Salim Yusuf, from McMaster University, Ontario, Canada, said: "The general public should ensure that they get about six to eight hours of sleep a day.

"On the other hand, if you sleep too much regularly, say more than nine hours a day, then you may want to visit a doctor to check your overall health.

"For doctors, including questions about the duration of sleep and daytime naps in the clinical histories of your patients may be helpful in identifying people at high risk of heart and blood vessel problems or death."

The team also found a 9% increased risk for people who slept a total of six or fewer hours, but this finding was not statistically significant.